322 Mr. J. W, Kirkby on Pei-mian Entomostraca 



For the convenience of those who may find fossil Entomos- 

 traca, or other small organisms, in a similar matrix to that in 

 which the Tunstall specimens occurred, it may be well to add a 

 word or two as to the mode I adopted for extracting the Permian 

 specimens from the calcareous dust. I first sifted the dust of 

 all the coarser particles — of everything larger than the tenth of 

 an inch ; and from what was left I took all the very fine dust 

 with another sieve, leaving a residue among which everything 

 organic could easily be distinguished. In picking out the or- 

 ganisms, a piece of polished slate — a common school slate, for 

 instance — is a good area on which to strew a portion of the 

 residue for examination. It is much better to adopt this method 

 than to pick the specimens out of a mass of material ; for by 

 sprinkling a small portion over the slab, every individual particle 

 can be recognized, and the organic forms separated from the 

 inorganic with very little trouble. A pair of blunt forceps with 

 broad points are exceedingly useful for picking up the specimens. 

 Some care is necessary, or injury may result to the specimens ; 

 but, with caution and a little skill, the forceps can be used with 

 a great delicacy of touch, and with less risk than the fingers. 

 Dr. Carpenter recommends the use of the moistened tip of a 

 camel's-hair pencil in similar cases; and in instances where the 

 objects sought ai"e extremely delicate, it will be the more prefer- 

 able instrument : but when the specimens, like the Permian 

 Entomostraca, possess a moderate degree of firmness, they may 

 be extracted with greater ease and celerity as above indicated ; 

 and when an extensive series of examples is needed, expedition 

 is of some value. With the assistance of a common lens and a 

 I)air of moderately good eyes, nothing more is required. It is 

 perhaps best to pick out a quantity of specimens " in rough," 

 and separate the specific forms afterwards. 



Genus Cythere, Miiller. 



Subgenus Bairdia [M'Coy], Jones, Entomostraca of the Cre- 

 taceous Formation of England. 



Syn. Genus Bairdia, M'Coy, 1844, Syn.Char. Carb.Foss. of Ireland. 



This group was instituted by Pi-of. M'Coy in 184t for the 

 reception of two species of Entomostraca from the carboniferous 

 rocks of Ireland, which he considered to differ generically from 

 any existing genus*. 



Mr. Rupert Jones, in his IMonograph of the Entomostraca of 

 the Cretaceous Formation of England, 1818, proposed its adop- 

 tion as a subgenus of Cijthcre, giving a good definition of its 



* Synopsis of the Chiuactcis oi" tlie Carboniferous Fossils of Ireland, 

 pa}j;c 164. 



